1. Field of the Invention
The invention relates in general to a type of audio-video signal transceiving processing device and more particularly to a type of audio-video signal transceiving processing device that decodes received analog video signals and analog audio signals into digital video signals and digital audio signals and outputs them to the computer.
2. Description of the Related Art
In technology advanced era nowadays, computers have become an indispensable part of the everyday life of modern people. Because computers can only play digital audio-video (AV) signals, analog signals from television (TV) stations can not be played directly on computers. Therefore, some manufactures developed AV signal transceiving processing devices which can transform the analog signals into digital signals that can be played on computers.
Widely used AV signal transceiving processing devices nowadays are TV tuner cards, which are also called TV capture cards. The user can view the television signal on the computer monitor by having a TV tuner card. However, ordinary TV tuner cards have PCI interface. They are mainly used in desktop personal computers (PCs), and do not support hot plug. In the other hand, a new type of TV tuner cards have CardBus bus interface, and are mainly used in laptop PCs (as shown in FIG. 1). They do support hot plug, but they use hardware encoding method to process signals, therefore require more hardware components and have higher cost.
Please refer to FIG. 1 which is a circuit block diagram of traditional AV signal transceiving processing device. In FIG. 1, AV signal transceiving processing device 10 includes a video & audio encoder (AV encoder) 18, a CardBus bus interface 13, a video decoder 11, an audio decoder 16, a tuner 15, a multiplexer 17, and an audio analog-to-digital converter (ADC) 12. Wherein, the audio decoder 11 can be Philips SAA7113 decoder, the audio ADC 12 can be AKM5355 analog-to-digital converter, and the AV encoder 18 can be Fujitsu MB86393A Mpeg2 encoder. In addition, the tuner 15 can be Sony's tuner, and the audio decoder 16 can be AN5833 SAP decoder.
The tuner 15 is used to receive an analog TV AV signal T, and output an analog video signal Va, and an analog audio medium frequency signal Aa. The video decoder 11 is used to receive analog video signal Va, and output a digital video signal Vd to the AV encoder 18 accordingly. The audio decoder 16 is used to receive and decode an analog audio medium frequency signal Aa. Then, audio decoder 16 outputs an analog right channel audio signal AaR1 and an analog left channel audio signal AaL1 to the multiplexer 17.
The video decoder 11 can receive an analog signal from a video cassette recorder (VCR) such as an analog S video signal Vas or an analog V video signal Vav. The multiplexer 17 can receive an analog right channel audio signal AaR2 and an analog left channel audio signal AaL2, which correspond to the analog S video signal Vas and the analog V video signal Vav respectively, from the VCR. Video decoder 11 can receive the analog S video signal Vas or the analog V video signal Vav, and output a digital S video signal Vds or a digital V video signal Vdv accordingly. The multiplexer 17 outputs an analog right channel audio signal AaR and an analog left channel audio signal AaL, according to the analog right channel audio signal AaR1 and the analog left channel audio signal AaL1, or the analog right channel audio signal AaR2 and the analog left channel audio signal AaL2, to audio ADC 12. The audio ADC 12 is used to receive the analog right channel audio signal AaR and analog left channel audio signal AaL, and output a digital audio signal Ad to the AV encoder 18 accordingly.
The AV encoder 18 receives and encodes the digital video signal Vd and digital audio signal Ad, and outputs a digital AV signal X, for example a Mpeg2 AV signal, accordingly. Furthermore, the AV encoder 18 can receive and encode the digital audio signal Ad, the digital S video signal Vds or the digital V video signal Vdv, and output another digital AV signal Y, for example another Mpeg2 AV signal, accordingly. The AV encoder 18 transfers the digital AV signal X or Y to a computer 14, for example a laptop computer, through a CardBus bus interface 13. At this moment, the computer 14 can store or play the digital AV signal X or Y.
From the description above, it can be known that the AV signal transceiving processing device 10 must use several hardware components including the video decoder 11, the audio decoder 16, the audio ADC 12 and the AV encoder 18, to encode raw data, such as analog AV video signals and analog audio signals, into digital AV signals and output the digital AV signals to the computer 14. However, because the number of required hardware components is high, and the source of different components are different, the cost of the AV signal transceiving processing device 10 is relatively high.